Gas-filled surge diverter with electrode connections in the shape of band-type clips

ABSTRACT

In order to simplify the mountability of electrode terminals in the form of band-like clips on either two-electrode or three-electrode arresters, the clips are resiliently fashioned in a circumferential direction. When such a clip axially projects beyond a foot part of the respective end electrode, the projecting region in a three-electrode arrester can be part of a short-circuit device which electrically connects to the middle electrode, potentially in combination with an auxiliary discharge path.

BACKGROUND OF THE INVENTION

The invention is in the field of over-voltage protection forcommunication networks and is concerned with the structural design ofthe power feed elements to the electrodes of a gas-filled surgearrester.

For protection against over-voltages as can occur, among other things,due to lightning strikes, gas-filled surge arresters are employed incommunication networks and the appertaining devices that comprise one ortwo or, respectively, three discharge paths and, for this purpose, arecomposed of two end electrodes and, potentially, of a further electrodein the form of a middle electrode as well as of one or twohollow-cylindrical ceramic insulators.

In two-electrode surge arresters, the ceramic insulator usually has itsend face soldered to the end electrodes (see U.S. Pat. No. 4,266,260 A).In three-electrode surge arresters, the ceramic insulators are solderedat their circumferential end faces to both the middle electrode as wellas to a respective end electrode (see U.S. Pat. No. 3,885,203 A and U.S.Pat. No. 4,212,047 A). The contacting of the electrodes at their outercircumference usually occurs either within a housing with the assistanceof resilient clamps or with the assistance of leads that have their oneend soldered or welded tangentially, radially or axially to a respectiveelectrode and have their other end provided with a pluggable contactelement or fashioned for a soldering (see U.S. Pat. No. 4,212,047 andU.S. Pat. No. 4,984,125 A). In order to fashion the power feed elementsin gas-filled surge arresters of the higher performance category so thatthey are also sure to withstand extreme current loads, it is also knownto employ power feed elements in the form of a band-like clip that arefixed to the circumference of the surge arrester with a releasable clampclosure. A riveting or an ultrasound welding also come intoconsideration as a non-releasable clamp closure. In addition, theband-like clips can be fashioned so broad that they embrace not only theelectrically conductive foot region of the respective end electrode butalso the adjoining ceramic insulator over a respective part of the axiallength of the insulator. As a result thereof, the electrical behavior ofthe surge arrester can be positively influenced (see DE 196 41 385A1/U.S. Pat. No. 5,768,082 A).

It is also known to arrange additional component parts at the face endof the end electrodes of three-electrode arresters in order to realize ashort-circuit device (fail safe mechanisms) and/or in order to connectauxiliary discharge paths electrically parallel to the gas dischargepaths. For radial fixing of the component parts, specific designs in thefoot region of the end electrodes and a cap that resides under theinfluence of a spring and is electrically connected to the middleelectrode of the surge arrester are employed (see U.S. Pat. No.5,388,023 A; U.S. Pat. No. 5,633,777 A and U.S. Pat. No. 4,984,125A/FIG. 1a).

SUMMARY OF THE INVENTION

For a gas-filled surge arrester having band-like clips, the invention isbased on the object of simplifying the mountability of the band-likeclips and to thereby expand their function as far as possible.

For achieving this object, it is first provided that each clip allocatedto an end electrode is resiliently fashioned in the circumferentialdirection. This can be realized, for example, in that clip is providedwith a two-leg, clamp-like batter or bend. The clip can also be lent theform of a cap that comprises a hollow-cylindrical edge region and aplanar cover region provided with a center opening, whereby the edgeregion has its circumference provided with a plurality of bead-likeimpressed portions that lie against the foot part of the respective endelectrode. Given such a design of the clip, the electrical terminal ofthe respective end electrode can be prefabricated in the framework of anautomatic manufacturing sequence and can also be slipped onto therespective end electrode. The spring tension of the clip therebysuffices in order to assure a reliable contacting of the respective endelectrode given normal and medium current load.

A clip fashioned according to the invention can also exercise otherfunctions when it is utilized for contacting given three-electrodearresters and is fashioned broad enough. In this case, the clip can beput in place on the surge arrester so that the chip projects axiallybeyond the foot part of the respective end electrode by a certainlength. Parts of a short-circuit device electrically connected to themiddle electrode can be allocated to this projecting region of the clip,as can, additionally, parts of an auxiliary discharge path connectedelectrically parallel to the gas discharge path. To this end, a fusiondisk and a spacer are arranged within the projecting region of the clip.With a clip with a clamp-like batter or bend, a disk-shaped auxiliaryelectrode can also be allocated to the clip and has a diameter of atleast equal to the outside diameter of the clip. The auxiliary electrodeis held spaced from the edge of the clip by the fusion disk and thespacer and is pressed against the spacer by a spring. This spring can bea matter of a known spring clip (see FIG. 1 of U.S. Pat. No. 4,984,125).However, a coil spring or a spring washer can also be employed and isfixed by a U-shaped shackle secured to the middle electrode. In a knownway, the spacer holding the disk-shaped auxiliary electrode spaced fromthe edge of the clip can be an insulating member or—preferably—avaristor (see FIG. 1 of U.S. Pat. No. 5,388,023).

Instead of a disk-shaped auxiliary electrode, a cap-like auxiliaryelectrode (similar to part 37 of FIG. 3 of U.S. Pat. No. 5,633,777 andpart 15 of FIG. 1 of U.S. Pat. No. 5,388,023) can also be provided andis under the influence of a spring clip electrically connected to themiddle electrode. The cap-like electrode has an edge projecting into theprojecting region of the clip, accepts the fusion disk and the spacer,and is held insulated and spaced from the clip by a ring-like insulatorpart.

In the case of a clip in the form of a cap, the short-circuit device isformed by the planar cover surface of the cap and by a free end of aspring clip which is connected to the center electrode and which freeend engages into the center opening of the cap. The free end of thespring clip is held spaced from the planar cover surface of the cap bymeans of a fusion disk and the auxiliary discharge path that arearranged within the cap, and the fusion disk or the auxiliary dischargepath is insulated from the planar cover surface of the cap by means ofan insulating centering member. The auxiliary discharge path is composedof a varistor that is arranged in the cap and insulated from the cap bythe insulating centering member. However, a perforated mica folium canalso serve as auxiliary discharge path and the fusion disk, which liesthereagainst, is insulated from the cap.

A number of exemplary embodiments of surge arresters fashioned accordingto the invention are shown in FIGS. 1 through 8.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a three-electrode arrester with a firstembodiment of clip allocated to the end electrodes;

FIG. 2 is a perspective view of a two-electrode arrester with a firstembodiment of clip allocated to the two electrodes;

FIG. 3 is a partial side view with portions broken away of athree-electrode arrester having clips according to FIG. 1 and with theshort-circuit device, which is combined with an auxiliary dischargepath, being allocated to an end electrode;

FIG. 4 is a partial side view with portions broken away of amodification of the device of FIG. 3 with an auxiliary electrodefashioned as cap;

FIG. 5 is a partial side view with portions broken away of anothermodification of the device of FIG. 3 with rigid retainer shackle for theshort-circuit device and a spring washer allocated to the auxiliaryelectrode;

FIG. 5A is a side view of the spring washer in a relaxed condition;

FIG. 6 is a perspective view of a two-electrode arrester with a secondembodiment of a clip to be allocated thereto;

FIG. 7 is a perspective view of a three-electrode arrester with clips inthe form of a cap allocated to the end electrodes; and

FIG. 8 is a partial side view with portions broken away of athree-electrode arrester with clips according to FIG. 7 and with theshort-circuit device, which is combined with an auxiliary dischargepath, being allocated to an end electrode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a schematic illustration of a three-electrode arrester 1that comprises the two ceramic insulators 11 and 12 at both sides of amiddle electrode 13 and on whose one end electrode (not shown) anelectrical terminal in the form of a tightly fitting clip 2 is put inplace. An identical clip 2 is shown next to the end electrode 14. Thisclip, which is composed of an annular metal band 21 whose ends aresoldered or welded to form a radially projecting terminal 22, has itscircumference provided with a two-legged, clamp-like batter orprotrusion 23 lying approximately opposite the terminal 22, as a resultwhereof the clip 2 is rendered resilient in a circumferential direction.The clip can be slipped onto the flange-like foot part 15 of the endelectrode 14, whereby the dimensions of the foot part 15 of the endelectrode 14 and of the clip 2 are selected so that an adequate contactpressure is established. In particular, the diameter of the foot part 15should be slightly larger than the diameter of the ceramic insulator 11or, respectively, 12.

FIG. 2 shows a two-electrode arrester that comprises a ceramic insulator31, a first end electrode 33 as well as a second end electrode (notshown in detail) and a resiliently fashioned clip 2 is put in place oneach end electrode.

FIG. 3 shows portions of a three-electrode arrester according to FIG. 1that is augmented by a short-circuit device and combined with auxiliarydischarge paths. In this case, the width b of the clip 24 put in placeonto the foot 15 of the end electrode 14 is selected so large that theclip not only embraces a part of the surface of the ceramic insulator 12but also projects axially beyond the end electrode 14. As a resultthereof, a cylindrical space is formed in which a disk 4 of a fusiblematerial and a spacer 5 in the form of a varistor are arranged. Thespacer 5 is arranged and centered within the clip 24 by means of arubber-like ring 6. The assembly composed of the fusion disk 4 and thevaristor 5 also has a centrally perforated auxiliary electrode 7allocated to it and the electrode 7 lies against the spacer/varistor 5and is held by the free end of a spring clip 8 fixed to the middleelectrode 13. The fusion disk 4 melts in case of an overload, whereuponthe auxiliary electrode 7 contacts the edge of the clip 24.

FIG. 4 shows a modification of the device of FIG. 3, whereby thecritical difference is that a cap-shaped auxiliary electrode 84 isprovided instead of a disk-shaped auxiliary electrode 7, a fusion disk41 and a spacer/varistor 5 are arranged in the auxiliary electrode 84and an edge 85 of the electrode 84 is residing opposite the foot part 15of the end electrode within the projecting region of the clip 24. Theauxiliary electrode 84 is arranged and centered by an insulating ring 10and is held spaced and insulated from the clip 24.

FIG. 5 shows another modification of the device of FIG. 3, whereby thecritical difference is that the contact to the middle electrode 13 isproduced via a non-resilient, U-shaped shackle 82 that presses a springwasher 83 against the auxiliary electrode 71. The spring washer 83,which is shown in its relaxed condition in FIG. 5A, lies against thedisk-shaped auxiliary electrode 71 that has both sides provided with acentering surface 73 for the centered allocation of the spring washer 83and a centering surface 72 for the centered allocation of thespacer/varistor 5 within the projecting region of the clip 24.

FIG. 6 shows a two-electrode arrester 3 with ceramic insulator 31 andend electrodes 33 and 34, whereby a clip 25 in the form of a cap with ahollow-cylindrical edge region 26 and a planar cover or end region 27provided with a center opening 28 is to be allocated to each electrode.The cap 25 is also implemented with a power terminal 29. In addition,the clip 25 has the circumference of the edge region 26 provided with aplurality of point-like or bead-like impressions 30 that, when the clipor cap 25 is slipped onto an end electrode, the cap resiliently pressesonto the foot region of the respective end electrode and forms a contacttherewith.

FIG. 7 shows a three-electrode arrester 1 on whose end electrodes arespective clip or cap 25 is put in place. According to FIG. 8, athree-electrode arrester according to FIG. 7 and the cap 25 can likewisebe part of a short-circuit device connected to the middle electrode 13and can potentially additionally be part of an auxiliary discharge pathconnected electrically parallel to the gas discharge path of thearrester. The cap 25 has adequate height h in order to be able toreceive a fusion disk 4 and a spacer 5 within the cap. The spacer 5 inthe form of a varistor is arranged upon employment of an insulatingcentering member 9 in order to suppress a short-circuit between the freeend 84 of the spring clip 8 and the cap 25 in the normal operatingcondition.

We claim:
 1. A gas-filled surge arrester comprising at least two endelectrodes with a flange-like foot part, each foot part being solderedto an end face of a hollow-cylindrical ceramic insulator, each foot partbeing embraced by an electrical terminal, each terminal being a cliptightly fitting the foot part, said clip embracing a part of the axiallength of the ceramic insulator adjacent to the foot part, each cliphaving a terminal projecting radially outward, and means being formed ineach clip to cause the clip to be resilient in a circumferentialdirection.
 2. A gas-filled surge arrester according to claim 1, whereinsaid means is a two-legged clamp-like bend formed in said clip.
 3. Agas-filled surge arrester according to claim 1, having a middle thirdelectrode in addition to the two end electrodes, each clip projectingaxially beyond the foot part of the respective end electrode, theprojecting region being a part of a short-circuit device electricallyconnected to the middle electrode.
 4. A gas-filled surge arresteraccording to claim 3, wherein parts of an auxiliary discharge circuitelectrically parallel to the gas discharge path is additionallyallocated to the projecting region of the clip.
 5. A gas-filled surgearrester according to claim 4, wherein the short-circuit devicecomprises a disk-shaped auxiliary electrode having a diameter at leastequal to the outside diameter of the clip, said auxiliary electrodebeing spaced from an edge of the clip by means of a fusion disk and aspacer, which are arranged within the projecting part of the clip, saidauxiliary electrode being pressed against the spacer by a spring.
 6. Agas-filled surge arrester according to claim 5, wherein the spacer is avaristor.
 7. A gas-filled surge arrester according to claim 5, whereinthe spring is fixed by means of a U-shaped shackle to the middleelectrode.
 8. A gas-filled surge arrester according to claim 7, whereinthe spring is a spring washer.
 9. A gas-filled surge arrester accordingto claim 7, wherein the spring is a coil spring.
 10. A gas-filled surgearrester according to claim 1, wherein the clip has the form of a capwith a hollow-cylindrical edge region and a planar cover region providedwith a central opening, and the means is the edge region being providedwith a plurality of bead-like, circumferentially spaced impressionslying against the foot part of the respective end electrode.
 11. Agas-filled surge arrester according to claim 10, wherein the clip isadditionally part of an auxiliary discharge path circuited electricallyparallel to the gas discharge path.
 12. A gas-filled surge arresteraccording to claim 10, which includes a middle electrode being arrangedbetween hollow-cylindrical ceramic insulators, the clip projectingaxially beyond the foot part of the respective end electrode and aprojecting region being part of a short-circuit device which iselectrically connected to the middle electrode.
 13. A gas-filled surgearrester according to claim 12, wherein the short-circuit device isformed by a planar cover surface of the cap and by an end of a springclip connected to the center electrode that is free and engaged into thecenter opening of the cap, the free end of the spring clip being heldspaced from the planar cover surface of the cap by means of a fusiondisk and the auxiliary discharge path being arranged within the cap andthe fusion disk and auxiliary discharge path being insulated from theplanar cover of the cap by means of an insulating centering member. 14.A gas-filled surge arrester according to claim 13, wherein the auxiliarydischarge path is composed of a varistor that is arranged and insulatedby means of the insulating centering member.
 15. A gas-filled surgearrester according to claim 1, wherein a middle electrode is arrangedbetween the hollow-cylindrical ceramic insulators, the clip projectingaxially beyond a foot part of the respective end electrode, a projectingregion being part of a short-circuit device electrically connected tothe middle electrode and the means is a two-legged clamp-like bend. 16.A as-filled surge arrester according to claim 15, wherein parts of allauxiliary discharge path circuited electrically parallel to the gasdischarge path are additionally allocated to the projecting region ofeach clip.
 17. A gas-filled surge arrester according to claim 16,wherein the short circuit device comprises a disk-shaped auxiliaryelectrode having a diameter at least equal to the outside diameter ofthe clip, said auxiliary electrode being held spaced from the edge ofthe clip by means of a fusion disk and a spacer that are arranged withinthe projecting part of the clip and said auxiliary electrode beingpressed against the spacer by a spring.
 18. A gas-filled surge arresteraccording to claim 17, wherein the spacer is composed of a varistor. 19.A gas-filled surge arrester according to claim 17, wherein the spring isfixed to the middle electrode by a U-shaped shackle.
 20. A gas-filledsurge arrester according to claim 19, wherein the spring is a springwasher.